Field of the Invention
The present invention relates to an option device for an electrical appliance, which is mounted on the electrical appliance, and provided with a filter for purifying exhaust air from the electrical appliance, and an electric fan.
Discussion of the Background
Exhaust air from an electrical appliance such as an image forming apparatus contains ultrafine particles (UFP) such as siloxane which may be generated when silicon is heated, or hydrocarbon which may be generated when toner is melted at a high temperature. In recent years, regulations regarding such ultrafine particles are becoming strict. In view of the above, there is a demand for an electrical appliance, in which ultrafine particles in exhaust air are trapped by a filter or a like member, and purified air is discharged to the atmosphere. Design that satisfies such regulations has been applied to newly developed electrical appliances. Further, it is also possible to satisfy the regulations regarding ultrafine particles in exhaust air by mounting an option device for an electrical appliance provided with a function of purifying exhaust air as described above (hereinafter, simply called as an option device) on the existing electrical appliances. In this case, it is important to secure balance between the exhaust air flow rate from the electrical appliance, and the suction force by an electric fan in the option device. When the balance is not secured, the air flow inside the electrical appliance may be adversely affected.
As a conventional art related to adjustment of flow of exhaust air from an electrical appliance, Japanese Unexamined Patent Application Publication No. 2013-148299 describes a ventilation device provided with an air intake fan and an exhaust fan. The ventilation device is provided with an openable/closable plate for communicating and blocking air flow in a pipe connection port each serving as a chamber-interior suction port and a chamber-exterior ejection port, and a gear motor for driving the openable/closable plates.
A ventilation device described in Japanese Unexamined Patent Application Publication No. 2013-104656 is provided with a fan motor, an opening adjustment means, and a heating means inside an air intake passage from an external air suction port to an external air blowout port. The ventilation device is configured to prevent dew condensation by heating a part of external air supplied from the external air suction port.
An image forming apparatus described in Japanese Unexamined Patent Application Publication No. 2011-180235 is configured such that exhaust air containing particles which are generated from a heater roller for fixation is allowed to pass through a filter member by a duct and by an exhaust fan, and is discharged from an exit. Controlling the amount of exhaust air passing through the filter member utilizing an initial burst phenomenon makes it possible to extend the life of the filter member which is easily affected by heat.
A radiation detection device described in Japanese Unexamined Patent Application Publication No. 2010-230430 is configured such that changing the intake amount of external air in accordance with the calorific value of a heat generating component disposed on an air passage makes it possible to efficiently cool the heat generating component.
As described above, when an option device provided with a function of purifying exhaust air is mounted on an electrical appliance (such as an image forming apparatus), it is important to secure balance between the exhaust air flow rate from the electrical appliance, and the suction force by an electric fan in the option device. For instance, when the suction force by the electric fan in the option device is larger than a set exhaust air flow rate from the exhaust port of the image forming apparatus, if the air flow rate in the vicinity of a fixing device is larger than the design air flow rate, the temperature of the fixing device may be lowered than a set temperature. This may make it difficult to sufficiently fix the toner. Conversely, when the suction force by the electric fan in the option device is smaller than the set exhaust air flow rate from the exhaust port of the image forming apparatus, it may be difficult to sufficiently exhaust air from the exhaust port of the apparatus main body due to the existence of the option device as a resistance. This may impair the cooling performance of the inside of the image forming apparatus.
When there are electrical appliances of different types having different exhaust air flow rates, as an electrical appliance (image forming apparatus) on which an option device is mounted, preparing option devices of different types having different suction forces in order to handle the different exhaust air flow rates of the electrical appliances is disadvantageous in the aspect of cost and maintenance service. It is desirable to make the suction force of a common option device variable in order to handle electrical appliances of different types.
Further, when one or both of the exhaust air flow rate of the electrical appliance, and the suction force of the option device varies accompanied by use, and as a result when it is difficult to secure balance between the exhaust air flow rate and the suction force, making the suction force of the option device variable makes it easy to secure balance between the exhaust air flow rate of the electrical appliance and the suction force of the option device again. It may be easy to solve the aforementioned drawback by variably controlling the rotational speed of the electric fan in the option device. However, the aforementioned configuration requires an electric fan whose rotational speed is variably controllable, and a control circuit for controlling the electric fan. This may increase the cost.